Head-up display light path system with crossed light path design, vehicle-mounted head-up display device, motor vehicle and light path system design method

Abstract

The invention discloses a head-up display light path system with a crossed light path design. The head-up display light path system comprises an image generation unit, a first free-form surface reflector, a second free-form surface reflector and a shading structural member, wherein the image generation unit is used for generating an image light beam to be projected; the first free-form surface reflector receives an image light beam generated by the image generation unit and performs first reflection; the second free-form surface reflector receives the reflected image light beam of the first free-form surface reflector and performs second reflection; the shading structural member is mounted on a light path among the image generation unit, the first free-form surface reflector and the second free-form surface reflector, and guides light propagation; light paths propagating between the first free-form surface reflecting mirror and the second free-form surface reflecting mirror are crossed under the guidance of the shading structural member. The invention further discloses a vehicle-mounted head-up display device and a motor vehicle, and the vehicle-mounted head-up display device and the motor vehicle have wide application value.

Description

Technical Field

[0001] This invention belongs to the field of vehicle head-up display technology, and relates to a head-up display optical path system with cross optical path design, a vehicle head-up display device, a motor vehicle, and a design method for the optical path system. Background Technology

[0002] As a core component of smart cockpits, the optimization of the optical path design of automotive head-up displays (HUDs) directly affects product size, image quality, and driving safety. In existing technologies, HUD optical path systems mostly employ non-intersecting parallel optical path designs. For example, Chinese invention patent application CN202011047223.5 (publication date: December 29, 2020) discloses an AR-HUD system based on a freeform surface mirror, where the optical paths of the large and small mirrors are parallel. Similarly, other existing technologies also exist. [1] A method to compress the optical path volume using double freeform surface mirrors was proposed, but it did not break through the limitations of the traditional non-intersecting optical path architecture.

[0003] The aforementioned prior art has the following drawbacks:

[0004] 1. Insufficient stray light suppression

[0005] Parallel optical paths result in excessively large apertures (typically >60mm), which can easily create reflection paths on the surface of the optical image source when sunlight flows back, propagating in the opposite direction to the driver's field of view. At the same time, if DLP or LCOS is used as the image generation unit, the scattered light from the diffuser that receives the optical image (the scattered light generated when external sunlight flows back onto the diffuser surface) can easily return along the original optical path, forming white spot glare at the driver's viewpoint and affecting image readability.

[0006] 2. Sunlight streaming in reverse

[0007] As the optical parameters of HUDs continue to increase (field of view, FOV), the optical magnification of the product will also increase. Therefore, the energy generated on the surface of the image source when sunlight shines back will also increase. This excessive irradiance may cause the image generation unit to exceed its maximum operating temperature and fail. Traditional HUD optical paths usually use a double protection method (dustproof film plus polarization, small reflector plus cold light) to reduce thermal risks. However, when facing larger optical sizes, relying on these two methods alone is insufficient to control the product failure risk caused by sunlight backflow.

[0008] 3. Low space utilization

[0009] Traditional parallel light path designs require reserving the distance between the optical components and the light beam. Due to the large volume of the light envelope itself, it is difficult to make a compact design, which restricts the application of HUD in small vehicles. Summary of the Invention

[0010] To address the shortcomings of existing technologies, the present invention aims to provide a head-up display (HUD) optical path system with a cross-beam optical path design, an in-vehicle HUD device, and a motor vehicle. The cross-beam optical path proposed in this invention, constrained by a light-shielding structure, forms a natural aperture at the intersection, allowing only a small portion of sunlight backflow to pass through, thus effectively mitigating the risk of sunlight backflow in large-size HUD products. Furthermore, this invention innovatively introduces a cross-beam optical path design between large and small reflectors, forming a natural aperture constraint at the intersection point. This breaks through the limitations of traditional architectures, significantly reducing stray light and the risk of sunlight backflow through geometric optical path optimization, while simultaneously achieving product size reduction, providing a new solution for in-vehicle HUD technology.

[0011] This invention provides a head-up display optical path system with a cross-optical path design, comprising: an image generation unit, a first freeform surface mirror, a second freeform surface mirror, and a light-shielding structural component; wherein,

[0012] The image generation unit is used to generate an image beam to be projected;

[0013] The first freeform surface mirror receives the image beam generated by the image generation unit and performs a first reflection;

[0014] The second freeform surface mirror receives the reflected image beam from the first freeform surface mirror and performs a second reflection;

[0015] The light-shielding structure is installed in the optical path between the image generation unit, the first freeform surface mirror, and the second freeform surface mirror to guide the propagation of light.

[0016] The light paths propagating between the first freeform surface mirror and the second freeform surface mirror intersect under the guidance of the light-shielding structure, forming a natural aperture.

[0017] In one specific embodiment, the image beam is reflected by the second freeform surface mirror and then incident on the vehicle windshield and reflected again, where it is captured by the driver's eye box area to see a virtual image.

[0018] The light-shielding structure is a one-piece molded or detachable optical light guide component, with an overall hollow shell shape forming a three-dimensional angled cavity that extends in a frustum-shaped manner at the front and back, and has multiple openings. An incident opening is provided at its bottom, through which the image beam generated by the image generation unit enters the light-shielding structure. Lateral openings are provided on both sides of the light-shielding structure, including a first lateral opening and a second lateral opening, respectively opposite the first freeform surface reflector and the second freeform surface reflector.

[0019] The optical path between the image generation unit, the first freeform surface mirror, and the second freeform surface mirror is matched with the internal structure of the light-shielding structure.

[0020] The light-shielding structure is made of non-reflective light-absorbing material and has a precisely controlled aperture to suppress stray light. Specifically, the structure of the light-shielding structure strictly matches the beam shape of the intersecting optical paths in the optical path system, and the aperture size of the light-shielding structure is increased by 2-5 mm based on the actual envelope size of the beam. The distance between the light-shielding structure and the first freeform surface mirror and / or the second freeform surface mirror is 3-10 mm.

[0021] The aperture shape of the light-transmitting part of the light-shielding structure can be rectangular, with a gap of about 2 to 5 mm reserved between the edge of the aperture and the outermost light ray; based on parameters such as the field of view (FOV) of the HUD system, the incident light diffusion angle, the size of the freeform mirror, and the position of the light path intersection, it is accurately determined through geometric optics simulation;

[0022] In one embodiment of the present invention, the image generation unit may select to employ a projection optical engine, including digital light processing (DLP) or liquid crystal silicon wafers, to generate an image to be projected;

[0023] In one embodiment of the present invention, the size of the second freeform surface reflector is larger than that of the first freeform surface reflector; specifically, the long side dimension of the second freeform surface reflector is in the range of 300-420mm, and the long side dimension of the first freeform surface reflector is in the range of 120-260mm.

[0024] In this invention, based on the principles of geometric optics, the surface parameters, position, tilt angle, and other parameters of the first and second freeform surface mirrors are calculated and determined after multi-objective optimization using the freeform surface optimization algorithm in the optical design software CODE V. The design and implementation of the cross optical path includes the following steps:

[0025] Step a: Construct an initial optical system comprising an image generation unit, a first freeform surface mirror, a second freeform surface mirror, and a windshield; the optical paths in the initial optical system are non-intersecting.

[0026] Step b: Set the image quality optimization goal and construct the optimization objective function;

[0027] Step c: Adjust the surface parameters, position, tilt angle, etc. of the first freeform surface mirror and the second freeform surface mirror so that the reflected light paths of the first freeform surface mirror and the second freeform surface mirror intersect in space;

[0028] Step d: Further optimize the geometric constraints of the intersection position through simulation to achieve a cross optical path that meets the requirements and optimize the space occupied.

[0029] In step b, the objective function is a single comprehensive optimization objective function (Merit Function), which includes one or more optical performance indicators and corresponding optimization objectives:

[0030] Modulation transfer function (MTF) ≥ 0.5;

[0031] Distortion <5%;

[0032] Field uniformity ≥ 80%;

[0033] Minimize optical path space occupancy;

[0034] Binocular parallax ≤ 2mrad;

[0035] The beam aperture at the cross position is strictly controlled to be ≤30mm.

[0036] In this invention, binocular parallax refers to the minute angular difference in the projection position of the virtual image onto the retinas of the left and right eyes when observing the virtual image projected by the HUD, due to the different positions (interpupillary distance) of the driver's left and right eyes. Excessive binocular parallax makes it difficult for the driver to fuse the two images seen by the left and right eyes into a single, clear image, resulting in double or blurry images. The brain needs to constantly try to fuse the non-overlapping images, which can lead to eye fatigue and headaches over time.

[0037] In one specific implementation, the allocation of the above weights is set with priority, and the priority order is as follows: binocular parallax; distortion control; modulation transfer function (MTF); beam aperture limitation; field uniformity; spatial volume minimization.

[0038] In step c, the first freeform surface mirror and / or the second freeform surface mirror both adopt an XY polynomial freeform surface mirror structure, wherein the highest order of the XY polynomial is less than or equal to 7; the specific parameters are automatically optimized and calculated using CODE V software.

[0039] The surface profile accuracy (PV) of the first freeform surface mirror and / or the second freeform surface mirror is less than 100 μm;

[0040] And / or,

[0041] The first freeform surface reflector and / or the second freeform surface reflector are installed and fixed by a spring clamp with a fine adjustment mechanism, which can simultaneously achieve fine adjustment of the position and tilt angle of the freeform surface reflector, and the installation accuracy is controlled within ±0.1° for its spatial position and tilt angle.

[0042] In step c, the optical path intersection between the first freeform surface mirror and the second freeform surface mirror is located near the midpoint; specifically, the optical path intersection is approximately 30% of the optical path length from the first freeform surface mirror to the second freeform surface mirror, closer to the first freeform surface mirror.

[0043] Furthermore, the optical path intersection position is approximately 50–100 mm from the surface of the first freeform surface mirror; the spatial position accuracy is controlled within ±10 mm; and this position can also be precisely controlled by optimizing the surface parameters of the freeform surface.

[0044] In step d, the scenario of sunlight backflow is simulated by geometric optics simulation, the geometric constraints at the intersection are optimized, the light flux of sunlight backflow through the intersection is significantly reduced, and the volume occupied by the control space is further optimized.

[0045] Based on the optimized optical path characteristics, design and install light-shielding structural components.

[0046] The beneficial effects of this invention include: the head-up display optical path system of this invention, by innovatively introducing an optical path crossing structure between freeform surface mirrors, can effectively reduce the light transmission aperture, thereby reducing the intensity of white spot glare, which can be reduced by more than 70% compared with the traditional parallel optical path system; since the optical path crossing structure in this invention naturally forms an aperture, it can reduce the amount of backflow sunlight to less than 50% of the traditional solution; in addition, due to the spatial folding caused by the optical path crossing, it can effectively reduce the optical path redundancy inside the optical path system, and the volume of the overall optical module can be compressed by 20-30%. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of a traditional HUD optical path;

[0049] Figure 2 This is a schematic diagram of the optical path of the present invention;

[0050] Figure 3 This is a schematic diagram of the head-up display optical path system with a light-shielding structure according to the present invention.

[0051] Figure 4 This is a schematic diagram of one angle of the light-shielding structure of the present invention.

[0052] Figure 5 This is a schematic diagram of the light-shielding structure of the present invention from another angle.

[0053] Figure 6 This is a schematic diagram of the light-shielding structure of the present invention from another angle.

[0054] In the figure, 1-image generation unit, 2-first freeform surface reflector, 3-second freeform surface reflector, 4-light-shielding structure, 41-incident opening, 42-first lateral opening, 43-second lateral opening, 5-windshield, 6-driver's eye box. Detailed Implementation

[0055] The present invention will be further described in detail below with reference to the specific embodiments and accompanying drawings. Except for the contents specifically mentioned below, the processes, conditions, and experimental methods for implementing the present invention are all common knowledge and general knowledge in the art, and the present invention does not have any particular limitations.

[0056] This invention addresses the technical bottlenecks of existing automotive head-up display (HUD) optical path systems by proposing solutions to the following key issues:

[0057] Suppressing stray light and white spot glare: This addresses the risk of internal stray light caused by excessively large apertures (>60mm) in traditional parallel optical paths, especially the white spot glare caused by scattered light from the diffuser of the image generation unit (such as DLP / LCOS) returning along the original optical path when sunlight flows back, thereby improving the contrast and readability of the virtual image.

[0058] Reduce the risk of thermal failure caused by sunlight backflow: To address the problem of sunlight backflow energy accumulation caused by increased optical magnification in large field-of-view HUDs, we break through the limitations of traditional double-insurance solutions (dustproof film + polarizing film / small reflector coated with cold light film). By using an optical path cross design to form a natural aperture, we reduce the amount of sunlight backflow light to less than 50% of the original design, thus preventing the image generation unit from failing due to excessive irradiance and overheating.

[0059] Achieving compact optical modules: Overcoming the problem of excessive product size caused by redundant optical path and optical envelope volume limitations in traditional parallel optical paths, the optical module volume is reduced by 20%-30% through the spatial folding characteristics of cross optical paths, meeting the stringent requirements of small vehicle models for HUD installation space.

[0060] This invention systematically solves the aforementioned problems through an innovative optical path intersection architecture of large and small reflectors. While improving optical performance, it provides a technological foundation for the lightweight, high reliability, and scene adaptability of automotive HUDs. This invention utilizes the optical design software CODE V to specifically optimize the optical path of conventional AR-HUD systems. Through geometric optics analysis, the curvature and higher-order coefficients of the freeform surface are calculated and modified to achieve the intersection of optical paths between the large and small reflectors. Due to the characteristics of the optical path intersection, the HUD system designed in this invention not only saves internal space but also offers significant advantages and benefits in preventing sunlight backflow and white spot glare caused by diffuser scattering by adding light-shielding structural components. This invention is applicable to intelligent cockpit systems and enhances the driving experience of HUD products.

[0061] This invention provides a head-up display (HUD) optical path system with a cross-beam design. Its core technical measure is to achieve beam path intersection between large and small reflectors through optical optimization. The specific technical solution is detailed below:

[0062] I. Overall Architecture and Core Components

[0063] The cross-design head-up display optical path system of the present invention mainly consists of an image generation unit (PGU) 1, a first freeform surface reflector 2, a second freeform surface reflector 3, a light-shielding structure 4, etc., and may also include a windshield 5 that reflects image light into the human eye.

[0064] The image generation unit 1 can use existing optical-mechanical display units such as DLP or LCOS to generate the image to be projected; the first freeform surface mirror 2 and the second freeform surface mirror 3 are optical core devices, and the light cross path is realized through special optical optimization; the light shielding structure 4 is installed on the propagation light path to guide the propagation of light; and the windshield 5 serves as the carrier of the final imaging surface, reflecting the virtual image to the driver's eyes.

[0065] In one embodiment of the present invention, the size of the second freeform surface reflector 3 is larger than that of the first freeform surface reflector 2; specifically, the long side dimension of the second freeform surface reflector 3 is in the range of 300-420mm, and the long side dimension of the first freeform surface reflector 2 is in the range of 120-260mm.

[0066] II. Freeform Surface Optical Optimization Design

[0067] This invention utilizes the optical design software CODE V, and through the principles of geometric optics and freeform surface optimization algorithms, implements the following steps to realize the intersecting optical path:

[0068] Step a: Establish the initial optical path structure:

[0069] In CODE V, an initial optical system consisting of an image generation unit 1, a first freeform surface mirror 2, a second freeform surface mirror 3, and a windshield 5 is constructed. The initial design is a conventional non-intersecting optical path layout.

[0070] Step b, Goal setting and Merit Function construction:

[0071] Construct an optimization objective function to achieve image quality optimization, optical volume compression, and sunlight backflow suppression; the optical performance indicators to be optimized in the objective function include, but are not limited to, MTF (modulation transfer function), distortion, field uniformity, optical path space occupancy, binocular parallax, and beam aperture limitation in the beam crossing area;

[0072] Step c, Optimization of the light beam intersection structure:

[0073] The software introduces freeform surface XY polynomial higher-order coefficients (up to order 7) adjustment. By changing the curvature, position, tilt angle and higher-order polynomial coefficients of the first freeform surface mirror 2 and the second freeform surface mirror 3, a light path intersection structure is established between the first freeform surface mirror 2 and the second freeform surface mirror 3.

[0074] Specifically, by adjusting the radius of curvature and higher-order coefficients of the freeform surface, the reflected light path of the first freeform surface mirror 2 and the reflected light path of the second freeform surface mirror 3 are made to intersect each other in space, and the intersection position of the light paths is precisely controlled within a pre-designed specific area.

[0075] In one specific embodiment, the optical path intersection position is specifically: about 30% of the optical path length between the first freeform surface mirror 2 and the second freeform surface mirror 3, and about 50 to 100 mm away from the surface of the first freeform surface mirror 2; the spatial position accuracy is controlled within ±10 mm.

[0076] In this invention, the first freeform surface mirror 2 and / or the second freeform surface mirror 3 are automatically optimized using CODEV software to obtain accurate radii of curvature and higher-order polynomial coefficients.

[0077] At the same time, a commonly used high-precision spring mechanical clamp is used to fix the rotating shaft of the reflector. The clamp has a fine adjustment mechanism, which can realize the fine adjustment of the position and tilt angle of the free-form surface reflector to meet the requirements of spatial positioning accuracy and image height adjustment function.

[0078] Step d, Establishment and optimization of natural aperture: A natural aperture is formed at the intersection of optical paths through structural design; the effect of the aperture on suppressing backflow of sunlight is confirmed through geometric optics simulation, and the geometric constraints at the intersection are repeatedly optimized so that the light flux of backflow of sunlight through the intersection is greatly reduced (to less than 50%), thus avoiding the image generation unit 1 from overheating due to excessive irradiance.

[0079] Achieving spatial compactness: By utilizing the spatial folding characteristics of the cross-optical path structure, the redundant optical path required by traditional HUD systems is reduced, thereby reducing the overall optical module volume by 20%-30%; during optical optimization, the volume occupied is controlled as one of the optimization objectives.

[0080] III. Design of Matching Structural Components (Light-Shielding Structural Components)

[0081] In the intersection area, based on the beam space structure formed by the intersection light path, a light-shielding structure 4 that is precisely matched with the light path is designed. This structure has a precise light-transmitting aperture to limit external stray light entering the HUD. Through precise mechanical structure design, this structure is installed at the intersection position and, together with the natural aperture, further enhances the ability to suppress stray light and sunlight backflow.

[0082] The light-shielding structure 4 is made of non-reflective light-absorbing material and has a precisely controlled light-transmitting aperture to suppress stray light. The structure of the light-shielding structure 4 strictly matches the beam shape of the intersecting optical paths in the optical path system. The aperture size of the light-shielding structure 4 is increased by 2 to 5 mm based on the actual envelope size of the beam.

[0083] The shape of the light-transmitting part of the light-shielding structure 4 can be rectangular; it is precisely determined through geometric optics simulation based on parameters such as the field of view (FOV) of the HUD system, the incident light diffusion angle, the size of the freeform mirror, and the position of the light path intersection.

[0084] In one specific embodiment, the light-shielding structure 4 is characterized by the following:

[0085] Materials: Black matte light-absorbing material (such as black engineering plastic surface sprayed with matte paint);

[0086] Aperture size: precisely controlled based on the actual envelope size of the beam plus an allowance of approximately 2–5 mm;

[0087] Shape: Precisely matches the shape of the beam in the intersecting optical path, typically rectangular;

[0088] Aperture influencing factors: It is highly related to the field of view (FOV) of the HUD system, the incident light diffusion angle, the size of the freeform mirror, and the optical path intersection position, and is accurately determined through geometric optics simulation.

[0089] While simple aperture light-shielding plate structures exist in the prior art, the innovations of the light-shielding structure 4 of the present invention include:

[0090] The light-shielding structural component 4 is designed to precisely match the geometric space of the intersecting optical paths;

[0091] Precisely control the aperture size and combine it with the natural aperture effect;

[0092] It can further reduce solar backflow energy by more than 40% based on existing technology, thereby reducing thermal risks;

[0093] By integrating the shape of the light-shielding structure 4 with the optical path, the light is contained within the light-shielding structure 4 as much as possible, thus achieving high-efficiency stray light suppression.

[0094] IV. Verification of the Effects on Sunlight Backflow and Stray Light Suppression

[0095] Ray tracing simulation was performed on the optimized optical path system to verify the suppression effect of stray light and sunlight backflow. The light energy distribution of external sunlight backflow was simulated by the CODE V stray light analysis module (e.g., non-sequence tracing tool), and it was confirmed that the light irradiance received by the image generation unit was effectively reduced. At the same time, the white spot glare returned to the driver's view from the diffuser surface was significantly reduced to less than 30% of that of the traditional system.

[0096] V. Image Quality Assurance

[0097] By further optimizing the surface parameters of the freeform mirror, with particular attention to distortion, MTF improvement and parallax reduction, we ensure that the cross-optical path can achieve ideal imaging quality in different fields of view. The optimization of the freeform mirror is achieved through the automatic optimization algorithm in CODE V, and the surface control accuracy meets the requirements of mass production (such as surface accuracy PV value less than 100μm).

[0098] VI. Final Verification and Implementation

[0099] After completing the design scheme, optical simulation software is used to comprehensively evaluate the overall optical performance and stray light suppression capability. After verifying that all technical indicators have met the target, optical prototypes are made and laboratory verification is carried out to complete the overall performance confirmation of the HUD system.

[0100] The specific technical solution of this invention, by innovatively realizing the spatial intersection of optical paths between free-form surface mirrors of varying sizes, breaks through the limitations of traditional optical path design and creatively forms a natural aperture and spatial folding structure. This fundamentally solves existing technical problems such as insufficient stray light suppression, high risk of sunlight backflow, and excessively large optical module size. Through optical simulation and experimental verification, its technical effect is significantly better than existing solutions, and it has high practical engineering application value. In addition, in actual use, the image generation unit (PGU) 1 will pre-adjust or mirror the image content to ensure that the image finally seen by the driver is completely consistent with the original design in terms of vertical position, without affecting the actual visual experience, thus solving the vertical flipping or mirror reversal effect of image position caused by the cross-optical path design.

[0101] Beneficial effects compared to existing technologies:

[0102] The cross-design head-up display (HUD) optical path system proposed in this invention, by innovatively introducing an optical path crossing structure between freeform surface mirrors of different sizes, has the following significant advantages compared to traditional non-crossing parallel optical path HUD systems:

[0103] I. Significantly enhanced suppression effect on stray light and glare from vitiligo.

[0104] Existing non-cross-parallel light path HUD systems, due to their large aperture (typically greater than 60mm), pose a significant risk of sunlight backflow in practical use. When sunlight enters the HUD light path through the windshield, the scattered light generated on the diffuser surface easily travels back along the original light path, forming noticeable white spot glare that interferes with the driver's vision. This invention, by designing a cross structure between the large and small reflectors to form a natural aperture, effectively reduces the aperture (controlling it to below 50mm). According to non-sequential ray tracing simulation data from CODE V software, the intensity of the white spot glare in this invention is reduced by more than 70% compared to traditional parallel light path systems, and virtual image contrast and image readability are significantly improved.

[0105] II. The risk of thermal failure caused by backflow of sunlight is effectively reduced.

[0106] In large field-of-view (FOV ≥ 9°) HUD products, traditional parallel optical path solutions typically employ additional polarizing films or cold light films to prevent image generation unit failure due to overheating. However, with increasing optical magnification, the irradiance caused by sunlight backflow increases rapidly, rendering traditional measures insufficient to guarantee product reliability. The cross-optical path of this invention naturally forms an aperture structure. Simulation calculations show that this aperture reduces the amount of backflow sunlight to less than 50% of traditional solutions, thereby reducing the thermal irradiance intensity on the image generation unit at its source, effectively controlling its operating temperature, and ensuring stable operation of the image generation unit even under harsh sunlight conditions.

[0107] III. The utilization rate of the product's internal space has been significantly improved.

[0108] Traditional parallel optical path designs occupy a large amount of internal space, severely limiting the application of HUD products in small vehicles with limited space. The cross-optical path structure of this invention effectively reduces internal optical path redundancy through spatial folding. Comprehensive geometric optical model simulation and structural layout analysis show that this invention can reduce the overall optical module volume of HUD products by 20%-30%, significantly improving the space adaptability and installation convenience of HUD products in compact vehicles.

[0109] In summary, the cross-beam HUD system of the present invention demonstrates significant technical advantages and engineering value over traditional beam HUD products in many aspects, such as suppressing stray light, reducing the risk of sunlight backflow, and achieving a compact spatial layout. It has significant innovation and practicality, and provides a new and efficient solution for the development of vehicle HUD technology.

[0110] Example

[0111] like Figure 2 As shown, this invention provides a head-up display (HUD) optical path system with a cross-optical path design. The system includes an image generation unit 1 (PGU, employing an image source such as DLP or LCOS), a first freeform surface mirror 2, a second freeform surface mirror 3, and a car windshield 5. The image light emitted by the image generation unit 1 is reflected for the first time by the first freeform surface mirror 2 and then propagates to the second freeform surface mirror 3. After a second reflection on the second freeform surface mirror 3, the light is further reflected by the windshield 5 and finally imaged from the driver's perspective to form a virtual image.

[0112] In this embodiment, the optical paths of the first freeform surface mirror 2 and the second freeform surface mirror 3 are specially designed to intersect in space. The specific implementation method is as follows:

[0113] (1) Using the optical design software CODE V, a preliminary structural model of the HUD optical system was established, including the basic layout of the above-mentioned image generation unit 1, the first freeform surface mirror 2, the second freeform surface mirror 3 and the windshield 5.

[0114] (2) Set the optimization objective function. The optimization objective function includes, but is not limited to, various constraints such as modulation transfer function (MTF), distortion control, field uniformity, optical path volume and beam aperture in the cross region of light rays.

[0115] (3) By adjusting the surface parameters, position, tilt angle, etc. of the first freeform surface mirror 2 and the second freeform surface mirror 3, specifically including curvature, tilt angle and higher-order terms of the freeform surface XY polynomial (the highest order can reach 7th order), a spatial light crossing structure is formed between the two mirrors.

[0116] (4) Figure 3 As shown, a natural aperture is set at the intersection of light paths, which is a light-blocking structure 4 with precisely controllable aperture size. The light-blocking structure 4 is made of non-reflective material and is installed in the area where the light rays intersect. It can effectively block stray light and harmful beams of light generated by backlighting, thus playing a natural light-blocking role.

[0117] Through the aforementioned cross-designed optical path structure, the HUD optical path system described in this embodiment achieves the following significant effects:

[0118] First, the cross-positioned aperture structure effectively reduces the stray light intensity inside the HUD system, especially the scattered light formed on the diffuser surface after direct sunlight enters the optical path. Simulation test results of this embodiment show that the stray light intensity is reduced by more than 70% compared to the traditional parallel optical path design of the HUD system, greatly improving the contrast of the virtual image and driving safety.

[0119] Secondly, the natural aperture structure can significantly reduce the amount of sunlight backflow into the image generation unit. Optical software simulation data shows that the amount of sunlight entering the PGU surface can be reduced to less than 50% of the traditional parallel optical path scheme, thereby effectively avoiding the risk of thermal failure of the PGU due to excessive irradiance and improving the reliability and durability of the product.

[0120] Furthermore, the cross-design significantly reduces the overall size of the HUD optical module. Through geometric optical simulation and spatial layout analysis comparing this invention with existing products, the overall volume of the HUD in this embodiment can be reduced by approximately 20%-30% compared to the traditional parallel optical path design, making it more suitable for application in space-constrained small vehicles and further expanding the market application scope of HUD products.

[0121] To further verify the technical effects of the embodiments of the present invention, a comparative experiment was conducted with existing technologies (such as the parallel optical path HUD system described in Chinese invention patent application CN202011047223.5):

[0122] Test Project Results of traditional parallel optical path scheme Results of the cross-optical path scheme of this invention Improvement rate Intensity of solar backflow (irradiance) Benchmark (100%) ≤50％ ≥50％ stray light white spot glare intensity Benchmark (100%) ≤30％ ≥70％ Overall size of HUD optical module Benchmark (100%) ≤80％ 20％～30％

[0123] In summary, the embodiments of the present invention provide a novel head-up display optical path structure. By innovatively introducing a cross-optical path layout, it achieves a significant reduction in stray light intensity, an effective solution to the problem of sunlight backflow, and a compact design of the HUD system's spatial layout.

[0124] This invention employs a cross-path design where light rays are restricted at the intersection by a natural aperture (i.e., a light-shielding structure), reducing the amount of sunlight filtering through and thus preventing excessive solar radiation from entering the image generation unit. This effectively reduces the temperature rise in the image generation unit caused by excessive irradiance, thereby minimizing the risk of device failure due to overheating.

[0125] The innovation in this respect lies in:

[0126] 1. Natural aperture: At the point where light paths intersect, a natural aperture effect is formed, helping to limit the amount of light entering the image generation unit. This design avoids reliance on additional hardware (such as separate light-shielding or heat dissipation structures).

[0127] 2. Space optimization: This design optimizes the optical path and reduces the product size by using optical path intersections without sacrificing optical performance.

[0128] 3. Reduce irradiance risk: By controlling the luminous flux at the optical path intersection, the impact of sunlight backflow on the image generation unit is reduced, the risk of thermal failure caused by excessive irradiance is reduced, and the system can still operate stably in high-temperature environments.

[0129] In summary, this design achieves multiple advantages in terms of space, structure, and thermal management by optimizing the optical path structure and cleverly utilizing optical principles.

[0130] References

[0131] [1] Chen Xiaowei, Cao Yan, Xue Jialong, et al. Optimization design of optical module for dual freeform head-up display system [J]. Progress in Laser & Optoelectronics, 2023. DOI:10.3788 / LOP213312.

[0132] In the description of this invention, it should be understood that the terms used to indicate orientation or positional relationships are based on the orientation or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0133] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0134] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0135] To simplify the disclosure of this invention, specific examples of components and arrangements are described. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0136] The scope of protection of this invention is not limited to the above embodiments. Any variations and advantages that can be conceived by those skilled in the art without departing from the spirit and scope of this invention are included in this invention and are protected by the appended claims.

Claims

1. A head-up display optical path system with a cross-optical path design, characterized in that, include: Image generation unit (1), first freeform surface mirror (2), second freeform surface mirror (3), light-shielding structure (4); wherein, The image generation unit (1) is used to generate an image beam to be projected; The first freeform surface mirror (2) receives the image beam generated by the image generation unit (1) and performs a first reflection; The second freeform surface mirror (3) receives the reflected image beam from the first freeform surface mirror (2) and performs a second reflection; The light-shielding structure (4) is installed in the optical path between the image generation unit (1), the first freeform surface mirror (2), and the second freeform surface mirror (3) to guide the propagation of light. The light paths propagating between the first freeform surface mirror (2) and the second freeform surface mirror (3) intersect under the guidance of the light-shielding structure (4).

2. The head-up display optical path system as described in claim 1, characterized in that, The image beam is reflected by the second freeform mirror (3) and then incident on the vehicle windshield (5) and reflected again, and is captured by the driver's eye box (6) area to see the virtual image.

3. The head-up display optical path system as described in claim 1, characterized in that, The light-shielding structure (4) is an integrally formed or detachable optical light guide component. It is in the shape of a hollow shell, forming a three-dimensional angled cavity. It extends in the shape of a frustum at the front and back and has an entrance opening (41), a first lateral opening (42), and a second lateral opening (43). The incident opening (41) is located at the bottom of the light-shielding structure (4), and the image beam generated by the image generation unit (1) enters the light-shielding structure (4) through the incident opening (41); the first lateral opening (42) and the second lateral opening (43) are respectively opposite to the first freeform surface mirror (2) and the second freeform surface mirror (3).

4. The head-up display optical path system as described in claim 1, characterized in that, The light-shielding structure (4) is made of non-reflective light-absorbing material, and its structure strictly matches the beam shape of the cross-beam path in the optical path system; the aperture size of the light-shielding structure (4) is increased by 2 to 5 mm based on the actual envelope size of the beam; the distance between the light-shielding structure (4) and the first freeform surface mirror (2) and / or the second freeform surface mirror (3) is 3 to 10 mm.

5. The head-up display optical path system as described in claim 1, characterized in that, The image generation unit (1) employs a projection optical engine including digital light processing (DLP) or liquid crystal silicon wafer type; And / or, Based on the principles of geometric optics, the surface parameters, position, and tilt angle parameters of the first freeform surface mirror (2) and the second freeform surface mirror (3) are calculated and determined after multi-objective optimization using a freeform surface optimization algorithm. And / or, The second freeform surface mirror (3) is larger in size than the first freeform surface mirror (2); The long side dimension of the second freeform surface mirror (3) ranges from 300 to 420 mm, and the long side dimension of the first freeform surface mirror (2) ranges from 120 to 260 mm.

6. The head-up display optical path system as described in claim 1, characterized in that, The first freeform surface mirror (2) and / or the second freeform surface mirror (3) both adopt an XY polynomial freeform surface mirror structure, wherein the highest order of the XY polynomial is less than or equal to 7. And / or, The surface profile accuracy (PV) of the first freeform surface mirror (2) and / or the second freeform surface mirror (3) is less than 100 μm.

7. A vehicle-mounted head-up display device, characterized in that, Including the head-up display optical path system as described in any one of claims 1-6.

8. A motor vehicle, characterized in that, This includes the head-up display optical path system as described in any one of claims 1-6, or the vehicle-mounted head-up display device as described in claim 7.

9. A design method for a head-up display optical path system based on cross-optical path optimization, characterized in that, Includes the following steps: Step 1: Establish an initial optical layout model including an image generation unit (1), a first freeform surface mirror (2), a second freeform surface mirror (3), and a windshield (5); Step 2: Set the image quality optimization target and construct a multi-objective optimization function. The function variables include modulation transfer function (MTF), distortion, field uniformity, optical path space ratio, binocular parallax, and beam aperture index. Step 3: Adjust the surface parameters, position and tilt angle of the first freeform surface mirror (2) and the second freeform surface mirror (3) so that the light paths between the first freeform surface mirror (2) and the second freeform surface mirror (3) intersect in space; Step 4: Further optimize the geometric constraints at the intersection through simulation to achieve a cross-optical path that meets the requirements; Step 5: Based on the optimized optical path characteristics, design and install the light-shielding structural components (4).

10. The method as described in claim 9, characterized in that, In step two, the optimization objectives of the multi-objective optimization function include: Modulation transfer function ≥ 0.5; Distortion <5%; Field uniformity ≥80%; Minimize optical path space occupancy; Binocular parallax ≤ 2mrad; The beam aperture at the intersection position is ≤30mm; And / or, In step three, the surface parameters include the radius of curvature of the freeform surface and the coefficients of the higher-order polynomial.

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